Southern swordtail fishes, which belong to the viviparous teleosts called Xiphophorus, are unique models for studies of evolution sex chromosomes. Monofactorial sex-determining systems, with either male or female being heterogametic sex, as well determination involving more than two chromosomes, found in swordtails and related species. Some species seem have originated by crossing between close...

Thermal tolerance parameters of swordtail (Xiphophorus maculatus) and platy (X. helleri) at three acclimation temperatures were determined in the study. The CTMin values 20, 24 28°C temperature 9.41,10.42 11.95°C respectively for 9.38,11.5 13.23°C swordtail, while CTMax 37.41, 39.19 40.52°C 36.94, 38.89 40.07°C swordtail. Accordingly, affected lower upper tolerances fish by 3-4 °C. ARR varied b...

For many species in nature, a sire's progeny may be distributed among a few or many dams. This poses logistical challenges--typically much greater across males than across females--for assessing means and variances in mating success (number of mates) and reproductive success (number of progeny). Here we overcome these difficulties by exhaustively analyzing a population of green swordtail fish (...

This experiment consisted of 75 different pairs composed of two male adults Xiphophorus helleri meeting each other twice. On the first occasion, one of the fish was familiarized with the meeting place for 3h (resident) while its opponent was familiarized with another aquarium (intruder). Upon dominance of one individual over the other, the pair members were separated and returned to their respe...

Sunlight exposure is strongly indicated as one of the important etiologic agents in human cutaneous malignant melanoma. However, because of the absence of good animal models, it has not been possible to estimate the wavelengths or wavelength regions involved. We have developed a useful animal model from crosses and backcrosses of platyfish (Xiphophorus maculatus) and swordtails (Xiphophorus hel...

A fish melanoma cell line, PSM-1, was established from a hereditary melanoma in an interspecific hybrid of Xiphophorus for cytogenetic studies of this melanoma system. An amelanotic melanoma was obtained from the tail fin of a melanotic F1 hybrid between a spotted platyfish (Xiphophorus maculatus) and an albino swordtail (Xiphophorus helleri). The tumor tissue was dissociated and cultured in Ea...

The fine structure and the composition of pteridine pigments of erythrophores in adults of the swordtail fish, Xiphophorus helleri, were studied by means of cytochemistry, paper chromatography, ionophoresis, centrifugal fractionation, and electron microscopy. It was found that water-soluble pigments of erythrophores consisted exclusively of pteridine derivatives including large amounts of droso...

Swordtails (Xiphophorus; Poeciliidae) have figured prominently in research on fish mating behaviours, sexual selection, and carcinogenesis, but their population structures and dispersal patterns have been relatively neglected. Using nine microsatellite loci, we estimated genetic differentiation in Xiphophorus helleri within and between adjacent streams in Belize. The genetic data were complemen...

A three-point linkage group comprised of loci coding for adenosine deaminase (ADA), glucose-6-phosphate dehydrogenase (G6PDH), and 6-phospho-gluconate dehydrogenase (6PGD) is described in fish of the genus Xiphophorus (Poeciliidae). The alleles at loci in this group were shown to assort independently from the alleles at three other loci--isocitrate dehydrogenase 1 and 2, and glyceraldehyde-3-ph...